Many methods of binding sheets of paper or other flat stock materials together as a unit have been developed in the past, including book binding, Velobinding.RTM., spiral binding, etc. Each method has its own advantages and disadvantages. Classic book binding, although preferred in many applications, requires equipment and manufacturing techniques that generally do not lend themselves to low volume binding, such as that required in small companies, offices, print shops, etc. Velobinding may be performed with equipment readily available to small offices or print shops. The bound unit produced by Velobinding requires a large margin on the left-hand side and does not allow the resulting unit to be easily laid open for viewing.
Spiral binding allows a stack of papers to be bound together as a unit that is easily opened to any page, thus making it very acceptable in the marketplace. However, in the past the equipment required to spiral bind a stack of papers has not lent itself to application in small businesses, offices, print shops, etc., due to the expense and complexity of the binding equipment.
In spiral binding, a series of equally-spaced holes are punched in one edge of the stack of papers. A continuous spiral coil is then fed or spiraled through the holes to form a bound unit. Spiral binding has been a preferred method of binding for many years and a number of manufacturers sell equipment to perform spiral binding.
Typically, a pre-wound spiral coil is placed around an appropriately sized mandrel or a coil is wound over the mandrel. The stack of papers to be bound together is first punched along one edge and then positioned near the end of the mandrel. A roller is moved into contact with the outer surface of the spiral coil, pressing the inner surface of the coil against the mandrel. The free end of the spiral coil extending out from one end of the mandrel is manually placed within the first hole in the stack of papers. The roller is then rotated, causing the coil to rotate. As the roller rotates, the coil spirals into the holes in the stack of papers, binding them together as a unit. Exemplary prior art equipment used to perform spiral binding is disclosed in U.S. Pat. No. 4,378,822, issued to Morris and U.S. Pat. No. 4,249,278 issued to Pfaffle.
Most prior spiral binding equipment is large, complex, and designed for use in assembly lines where commercially produced spiral bound units are manufactured. Some prior art equipment is manufactured for use in smaller applications, such as offices, small businesses, or print shops. However, such equipment is expensive, and difficult and time consuming to use. Typically, one piece of equipment is purchased to punch appropriately spaced holes in the stack of papers and a second piece of equipment is purchased to spiral a coil into the stack of punched paper. In spiral binding equipment, such as that disclosed in the Morris patent, an operator manually positions a punched stack of papers so that the holes are positioned in line with a coil placed over a mandrel. The operator then manually starts the end of the coil into the holes in the paper. As described above, the operator then switches on the equipment so that a roller presses the coil against the mandrel, spiraling the coil into the holes in the paper.
During spiraling, it is common for the coil to deform slightly causing it to miss the holes in the paper, resulting in the coil binding or spiraling off the edge of the paper. One of the contributors to coil deformation is the fact that the coil is driven from only one edge of the paper, thus creating greater stresses within the coil as it spirals further along the length of the paper. When the coil binds or spirals off the edge of the paper, the rotation of the roller and coil must be reversed and the coil spiraled backward until it moves back into position. The spiraling process is then repeated until the coil spirals through all of the holes over the length of the stack of papers being bound.
If stacks of different thicknesses are to be bound together as a unit, the operator must maintain different size mandrels on hand. In order to use different size coils, it is necessary for the operator to exchange the mandrels in the apparatus to correspond with the size coil that is being used.
In other spiral binding equipment, the coil is started into the holes at one end of the stack of papers manually. The portion of the coil spiraled into the stack of papers is then pressed against two parallel, rotating rollers that extend along the edge of the stack of papers. As the coil is pressed against the moving rollers, the rollers contact the coil and spiral it into the holes in the paper. This type of spiral binding equipment also deforms the coil, causing it to miss holes in the stack of paper. Thus, an operator must reverse the rotation of the coil, reposition the coil and restart the operation.
Past spiral binding equipment is bulky, difficult to use, expensive, and poorly esthetically designed. In addition, prior spiral binding equipment has a number of moving parts. As with any equipment with moving parts, safety concerns are always an issue.
As can be seen from above, there is a need for improved methods and apparatus to spiral bind a stack of papers together as a unit. One goal of the present invention is to reduce some of the problems associated with prior apparatus and methods thus helping to meet this need.